CONSTRUCTIVE AND DESTRUCTIVE FORCES

1. Mountain Building All mountains have a history and there are many features of a mountain that provide information about that history. Lesson 1 Lesson 2 Lesson 3 Lesson 4 Lesson 5 Lesson 6 SHAPE ROCK COMPOSITION The shape of a mountain provides evidence about its formation and history. The shapes of mountains vary significantly. A rock's environment can modify it or completely transform it into something else. Rocks are categorized based on the most recent major change that occurred to them. Rocks have identifying characteristics that provide evidence of the changes that they have endured. The shape of non-volcanic mountains is determined by their tectonic setting. The shape of volcanoes is determined by the viscosity of the magma. Erosion changes rocks by breaking them down and moving them to different environments. Three main categories are igneous, sedimentary, and metamorphic. Where plates collide, compressional forces cause folded and thrust fault mountains. Where plates are pulling apart, tensional forces result in fault block mountains. CONSTRUCTIVE AND DESTRUCTIVE FORCES Erosion is a destructive force that sculpts and shapes all mountains. Geologic forces that form and shape mountains are both constructive and destructive. LOCATION Mountains tend to form near plate boundaries in long ranges that parallel the boundaries. Volcanoes form over subduction zones as continuous arc-shaped chains of volcanoes of different sizes. Mountains are usually made up of many types of rock. As plates move around over geologic time, plate boundaries change, resulting in modern day mountain belts that are far from present-day plate boundaries. Some rock types erode more easily than others, producing differential rates of erosion in neighboring rocks. Mountains composed entirely of volcanic rocks might be, but are not necessarily, volcanoes. Differential erosion of rocky material produces jagged mountains as well as batholiths, mesas and buttes.